1. Field of the Invention
This invention relates to a constant velocity ratio universal joint for torque transmission, comprising:
a hollow outer joint member having an internal surface with a number of grooves circumferentially spaced about the axis of rotation of the joint member and extending in meridian planes; PA1 an inner joint member disposed at least partially within the outer joint member and having an outer surface with a number of grooves circumferentially spaced about the axis of rotation of the joint member in meridian planes facing the grooves of the outer joint member in pairs, all the grooves in the joint members being undercut free; PA1 a plurality of balls received one in each facing pair of grooves in the joint members for torque transmission therebetween; PA1 the internal surface of the outer joint member between the grooves thereof being non-undercut, considered from one end of the member at which end the member has an internal diameter larger than at its other end, and including a part-spherical surface portion; PA1 the outer surface of the inner joint member between the grooves thereof having a part-spherical portion; PA1 and a cage of annular form disposed between the inner and outer joint members and having inner and outer part-spherical surface portions engaging said part-spherical surface portions of the inner and outer joint members, the cage holding the balls so that their centres occupy a plane guided to bisect the angle between the rotational axes of the inner and outer joint members. Such a constant velocity ratio universal joint will hereafter be referred to as a constant velocity ratio universal joint of the kind specified. PA1 the outer joint member is closed at said one end by a closure member; PA1 the inner joint member, at its end adjacent said one end of the outer joint member, has a part-spherical end surface engaged by a complementary support surface provided in association with said closure member; and PA1 the inner surface of the cage comprises said part-spherical portion which is engaged with the part-spherical surface portion of the inner joint member adjacent its other end, and which leads into a cavity extending to the end of the cage adjacent said one end of the outer joint member, said cavity having a size at least equal to the maximum diameter of the part-spherical inner surface portion of the cage and being undercut free considered from said end.
b 2. Description of Prior Art
A constant velocity ratio universal joint of the kind specified is disclosed in DE No. -2522670(GB No. 1553369). Both the ball-receiving grooves and the internal surface of the outer joint member therebetween, engaging the part-spherical outer surface of the cage, are of undercut-free configuration considered from one end of the outer joint member. The cage has a part-spherical internal surface which engages and axially fixes the cage relative to a part-spherical external surface of the inner joint member between the grooves thereof. The cage engages a separate guiding surface associated with the outer joint member. In such a joint, axial forces are transmitted in both directions between the joint members through the intermediary of the cage. Assembly of the cage to the inner joint member requires these parts to be placed in such a relative position that the inner joint member cannot be integral with a shaft part because the presence of the shaft part would interfere with the assembly operation, and hence a shaft part for transmitting torque to the inner joint member must be a separate component. This in turn requires the inner joint member to be provided with a bore for receiving a shaft component, and the inner joint member has to be of relatively large size to ensure that it has sufficient material for strength. Finally, close production tolerances are required in order to avoid noise during torque reversals and overloading of the cage, the latter requiring the radial thickness of the cage to be increased. It is not possible to produce the outside shape of the inner joint member and the inside shape of the cage without metal removal by machining the relevant surfaces of the components.